I am trying to set up filters on file extensions, and I read this article:
http://support.ipswitch.com/kb/IM-20010822-DM01.htm
The article says the filters search the body for the specified extension, but does that mean that even if someone just types "myfile.exe" and its not an actual attachement that it will be rejected?
That's not one of the best knowledge base articles -- it doesn't mention the drawbacks and variations. It only shows MIME, not uuencoded/BinHex/TNEF, and it shows the "na_me=" format rather than the "filena_me=" format (that has fewer false positives, but more false negatives), and just briefly mentions using quotations (which also has fewer false positives, but more false negatives).
The good news is that they won't catch just "myfile.exe" in an E-mail -- it would need the "na_me=" first (which is why I'm adding the underscores in there -- those filters would otherwise catch this E-mail). But, their .com filter will catch a lot of legitimate HTML E-mail, so you may want to avoid it.
As a number of people point out, for the most accurate trapping of file extensions you need AV software to handle the job, but for some people filtering is acceptable.
-Scott
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